The effect of partial substitution of Ca by Zn in Bi 1.7 Pb 0.3 Sr 2 Ca 2 − x Zn x Cu 3 O y at x = 0.00, 0.05, 0.10, 0.15 and 0.20 levels on the electrical and structural properties was investigated in this work. The characterization of the ceramics prepared by the conventional solid-state reaction method were done by resistance-temperature measurements, XRD, SEM and density analysis. Low levels of Zn substitution of Ca caused significant changes in the properties of the ceramics. The low-T c superconducting properties were enhanced and the fraction of the low-T c (2212) phase were found to increase at x = 0.15 level of Zn substitution at 830°C sintering temperature. Zero resistance was observed only in sample D with x = 0.15 and the T c was determined as 92 K. The SEM micrographs and the density analysis have shown that this was the densest packed ceramic.

In this work, the effects of quantum confinement on the ground state energy of a correlated electron–hole pair in a spherical and in a disc-like quantum dot have been investigated as a function of quantum dot size. Under parabolic confinement potential and within effective mass approximation Ritz's variational method is applied to Hylleraas-like trial wavefunction. An efficient method for reducing the main effort of the calculation of terms like rehk exp(−λreh) is introduced. The main contribution of the present work is the introduction of integral transforms which provide the calculation of expectation value of energy and the related matrix elements to be done analytically over single-particle coordinates instead of Hylleraas coordinates.

In this work, we propose an efficient method of reducing the computational effort of variational calculation with a Hylleraas-like trial wavefunction. The method consists of introducing integral transforms for the terms as r k 12 exp (−λr 12 ) which provide the calculation of the expectation value of energy and the relevant matrix elements to be done analytically over single-electron coordinates instead of Hylleraas coordinates. We have used this method to calculate the ground state energy of a two-electron system in a spherical dot and a disk-like quantum dot separately. Under parabolic confinement potential and within effective mass approximation size and shape effects of quantum dots on the ground state energy of two electrons have been investigated. The calculation shows that our results even with a small number of basis states are in good agreement with previous theoretical results.

In this study the electronic eigenstructure of an exciton in a parabolic quantum dot (QD) has been calculated with a high accuracy by using Finite element method (FEM). We have converted the coordinates of electron-light-hole system to relative and center of mass coordinate, then placed the Spherical Harmonics into Schrödinger equation analytically and obtained the Schrödinger equation which depends only on the radial variable. Finally we used FEM with only radial variable in order to get the accurate numerical results. We also showed first 21 energy level spectra of exciton depending on confinement and Coulomb interaction parameters.

The total dose absorbed on the tumor cell from the skin patch sources used in clinical superficial brachytherapy should be limited within the target tumor volume in order to minimize the potential side effects. Average range of the beta particles within tissue may exceed the thickness of a superficial skin tumor beyond the target tumor volume, causing side effects by damaging the deeper located healthy tissue and the bone underneath the tumor. It is desired to minimize the possible side effects by selecting a short-range radionuclide. Administering the treatment under an external magnetic field is another option for reducing side effects. To achieve this, in this study, the percentage deep dose (PDD) and transverse dose profile (TDP) distributions of the skin patch source labeled with Yttrium 90 (90Y) using the GEANT4-based GAMOS Monte Carlo code were examined before and after applying magnetic field, and it was evaluated  whether it was possible to limit the dose within a certain volume or not. Simulation results showed that, along with the application of a transverse magnetic field, the dose values increased by 7.2% and 3.1% respectively at 0.25 mm and 1.0 mm depths whereas it decreased by 9.4%, 25.0%, 41.8% and 57.6%, at 2.0 mm, 3.0 mm, 4.0 mm and 5.0 mm depths respectively on the central axis from the surface of the tissue phantom with respect to the 0 T values of the field.  In case of a superficial skin tumor with a thickness of 3.0 mm from the skin surface, the amount of dose accumulated in the tumor volume for 0 T value of the transverse magnetic field was 89% of the total dose, while it increased to 98% at the intensity of 1.5 T, and the dose received by the healthy tissue under the tumor decreased by 10.1%.